The unit of length convenient on the atomic scale is known as an angstrom and is denoted by Å: 1 Å = 10–10 m. The size of a hydrogen atom is about 0.5 Å. What is the total atomic volume in m 3 of a mole of hydrogen atoms ?
Radius of hydrogen atom, r = 0.5 = 0.5 × 10–10 m
Give four examples of physical quantities.
Examples of Physical quantitie are force, mass, density and power.
To get the complete knowledge of any physical quantity, measurement is needed. Measurement of any physical quantity involves comparison with a certain basic, arbitrarily chosen, internationally accepted reference standard called unit. Knowledge without measurement is incomplete and unsatisfactory.